1. Field of the Invention
The present invention relates to an ink, an ink-jet recording process using such an ink, a recorded article obtained by such a recording process and instruments using such an ink, and particularly to an ink which can enhance fluorescence intensity and provide a recorded article good in record quality including stability, reliability and coloring ability to look at, an ink-jet recording process using such an ink, a recorded article obtained by the recording process, and instruments using such an ink. The present invention also relates to a method of enhancing fluorescence of a fluorescent colored portion of a recorded article comprising a recording medium and the colored portion provided thereon, and a method of elongating the life time of fluorescence.
2. Related Background Art
Various investigations and reports have heretofore been made on inks for writing utensils and inks for ink-jet. In particular, in order to enhance the quality of recorded articles, including fluorescence intensity and coloring ability, such various proposals as described above have been made. For example, proposals of coloring materials and the like each having a novel structure, which are suitable for use in inks for the above-described use applications, proposals of inks using a coloring material (hereinafter referred to as xe2x80x9cfluorescent coloring materialxe2x80x9d) exhibiting fluorescence properties as a main coloring material, and proposals as to the combined use of a fluorescent coloring material as a coloring material for inks have been made. In particular, the proposals as to inks, which pay attention to the fluorescence properties of fluorescent coloring materials, include Japanese Patent Application Laid-Open Nos. 8-151545, 9-132729, 10-193775, 10-298462 and 10-298467, and Japanese Patent No. 233038, and novel recording processes and fluorescent coloring materials have been proposed therein.
In addition, the proposals as to the use of fluorescent coloring materials include Japanese Patent Application Laid-Open Nos. 5-293976, 6-191143, 6-322307, 7-009755, 7-305013, 8-053639, 9-003375, 9-01294, 9-137097, 9-137098, 9-137099, 9-165539, 9-241565, 9-255904, 9-286939, 10-007962, 10-183043, 11-080639, 11-320921 and 2000-038529, and Japanese Patent No. 2995853.
In recent years, the use applications of fluorescent coloring materials have not been limited to the mere formation of beautiful color images heretofore conducted, and there have been proposed, for example, technical development that fluorescence properties are imparted to an ink, information such as characters, numerals, marks and/or bar codes is recorded on a recording medium with such an ink, and the fluorescent ink is caused to emit light by irradiating the recording medium with ultraviolet light having a proper wavelength, thereby imparting another information (for example, security information) than visible information. Accordingly, there is room to widen the use applications of inks exhibiting fluorescence properties in many fields, and there is a strong demand for development of inks which are stable, reliable, high in fluorescence intensity and excelling in coloring ability.
With respect to the coloring ability of an ink on a recording medium, however, only chromaticity (L*,a*,b*) that is used as a measure of colors has heretofore been considered. Even when a fluorescent color material is used, design is also made according to the conventional measure under the circumstances. Therefore, it has been hard to say that the fluorescence properties of the coloring material are fully utilized. More specifically, even in the above-described various proposals making use of the fluorescent coloring materials, in the standpoint of the coloring ability of the coloring materials, the fluorescent coloring materials are used on the basis of only the viewpoint of (L*,a*,b*), not the viewpoint of the fluorescence properties, or attention is paid to the fluorescence properties of the coloring materials, but no attention is paid to the color developing properties of fluorescence, in other words, the interfacial properties of the fluorescence. Therefore, such proposals have not fully made the best use of the fluorescence properties of the coloring materials.
It is accordingly an object of the present invention to provide an ink which can provide a recorded article to the recorded portion of which, for example, fluorescence properties important for colors of the natural kingdom are sufficiently imparted fully making good use of the fluorescence properties of the ink, and which the recorded article has high fluorescence intensity and is excellent in print quality including coloring ability, said ink being capable of enhancing the stability and reliability of the recorded article.
Another object of the present invention is to provide an ink-jet recording process by which a recorded article having a fluorescent colored portion having high fluorescence intensity can be formed simply and stably.
A further object of the present invention is to provide a recorded article equipped with a colored portion having high fluorescence intensity.
A still further object of the present invention is to provide a recorded article having a fluorescent colored portion the fluorescence intensity of which is hard to be deteriorated with time.
A yet still further object of the present invention is to provide an ink-jet recording apparatus, an ink cartridge and a recording unit by which a recorded article having a fluorescent colored portion exhibiting excellent fluorescence intensity can be stably provided.
A yet still further object of the present invention is to provide a method of enhancing fluorescence of a fluorescent colored portion of a recorded article comprising a recording medium and the colored portion provided thereon, and a method of elongating the life time of fluorescence.
The above objects can be achieved by the present invention described below.
According to an embodiment of the present invention, there is thus provided an ink comprising
(i) first and second organic compounds which are incompatible with each other;
(ii) at least one of a compound exhibiting fluorescence properties and a coloring material exhibiting fluorescence properties; and
(iii) a liquid medium dissolving or dispersing the components (i) and (ii) therein.
The ink may further have a compound having a vapor pressure of not lower than that of diechyleneglycol.
The ink may be used as an ink for ink-jet.
According to another embodiment of the present invention, there is provided an ink-jet recording process, comprising the step of ejecting the ink for ink-jet described above from an orifice in response to recording signals.
According to a further embodiment of the present invention, there is provided a recorded article obtained by the ink-jet recording process described above, wherein the fluorescence intensity of a recorded portion formed on wood-free paper has a proportional relationship to the water content in the wood-free paper.
According to a still further embodiment of the present invention, there is provided a recorded article having a colored portion exhibiting fluorescence properties on a recording medium, wherein the colored portion contains at least one of a compound exhibiting fluorescence properties and a coloring material exhibiting fluorescence properties and has an interface between the outermost surface thereof and the surface of the recording medium, on which incident light on the colored portion from the outside is reflected.
According to a yet still further embodiment of the present invention, there is provided a recording unit comprising an ink container containing the ink for ink-jet described above and a head portion for ejecting the ink.
According to a yet still further embodiment of the present invention, there is provided an ink cartridge comprising an ink container containing the ink for ink-jet described above.
According to a yet still further embodiment of the present invention, there is provided an ink-jet recording apparatus comprising an ink container containing the ink for ink-jet described above and a head portion for ejecting the ink.
According to a yet still further embodiment of the present invention, there is provided a method of enhancing fluorescence of a fluorescent colored portion of a recorded article comprising a recording medium and the colored portion provided thereon, wherein the colored portion is formed by an ink-jet recording process comprising the step of applying an ink to a recording medium by an ink-jet system, and an ink comprising
(i) first and second organic compounds which are incompatible with each other;
(ii) at least one of a compound exhibiting fluorescence properties and a coloring material exhibiting fluorescence properties; and
(iii) a liquid medium dissolving or dispersing the components (i) and (ii) therein is used as said ink.
According to a yet still further embodiment of the present invention, there is provided a method of enhancing fluorescence of a fluorescent colored portion of a recorded article comprising a recording medium and the colored portion provided thereon, which comprises providing a reflecting interface for incident light on the colored portion from the outside between the outermost surface of the colored portion and the surface of the recording medium at the colored portion.
According to a yet still further embodiment of the present invention, there is provided a method of elongating the life time of fluorescence of a fluorescent colored portion of a recorded article comprising a recording medium and the colored portion provided thereon, wherein the colored portion is formed by an ink-jet recording process comprising the step of applying an ink to a recording medium by an ink-jet system, and an ink comprising
(i) first and second organic compounds which are incompatible with each other;
(ii) a compound having a vapor pressure not lower than that of diethyleneglycol;
(iii) at least one of a compound exhibiting fluorescence properties and a coloring material exhibiting fluorescence properties; and
(iv) a liquid medium dissolving or dispersing the components (i), (ii) and (iii) therein is used as said ink.